Hemostatic material

ABSTRACT

A new and improved hemostatic material formed of an oxidized cellulosic material and method for its preparation wherein an oxidized cellulosic material is treated with a borohydride under alkaline conditions.

Unite States Patent Briskin et al.

[151 3,666,750 51 May 30, 1972 [5 4] HEMOSTATIC MATERIAL [72] Inventors:Theodore S. Briskin, Beverly Hills; Allen 11. Remanick, Pasadena, bothof Calif.

[73] Assignee: Johnson & Johnson, New Brunswick, NJ. [22] Filed: Dec.15, 1969 [2]] Appl. No.: 885,313

[52] U.S. Cl ..260/212, 128/156, 128/325,

424/ 180 [51] Int. Cl ..A61l 15/00, C08b 15/02, C08b 23/02 [58] FieldofSearch ..260/212; 131/2; 128/325 [56] References Cited UNITED STATESPATENTS 3,122,479 2/1964 Smith ..128/325 Primary Examiner-Donald E.Czaja Assistant Examiner-Ronald W. Grifiin Attorney-Harold 1.. Warnerand Ralph T. Lilore ABSTRACT A new and improved hemostatic materialformed of an oxidized cellulosic material and method for its preparationwherein an oxidized cellulosic material is treated with a borohydrideunder alkaline conditions.

6 Claims, No Drawings This invention relates to materials for thecontrol of bleeding, and more particularly to hemostatic material formedof oxidized cellulose.

it is known that cellulosic material may be selectively oxidized withnitrogen dioxide to convert more than 90 percent of the methylol groupsin the cellulosic molecule to yield a product which may be referred toas an oxycellulose or polyuronic acid. It is similarly known, asillustrated by US. Pat. Nos. 1,197,400 and 2,232,990, that oxidizedcellulose may be used as a hemostatic material for the control ofbleeding. The use of oxycellulose as compared to other hemostaticmaterials heretofore known, such as conventional gauze pads and the liketreated with ferric chloride, thrombin, etc., represents a significantimprovement since oxycellulose may be left in a closed wound without theresult of a severe local tissue reaction in response to the presence offoreign material.

However, the primary disadvantage of hemostatic materials formed ofoxidized cellulose heretofore known is that they lack stability wherebythey must be used within a short time after manufacture, or they must bestored under refrigeration. Various attempts to overcome thisdisadvantage, such as by the washing of oxidized cellulose afteroxidation with an anhydrous alcohol as suggested by U.S. Pat. No.3,364,200, have been made. However, such attempts have generally beenunsuccessful in that the use of an anhydrous alcohol is expensive, anddoes not significantly increase the stability of the resulting oxidizedcellulose.

It is accordingly an object of the present invention to provide a newand improved hemostatic material formed of oxidized cellulose which isstable at room temperatures, and need not be stored under refrigeration.

It is another object of the present invention to provide a simple andinexpensive method for treating oxidized cellulose to improve thethermal stability of oxidized cellulose for use in hemostatic materials.

These and other objects and advantages of the present invention willappear hereinafter, and, it will be understood that the followingspecific examples are provided by way of illustration, and not by way oflimitation, of the concepts of the present invention.

The present invention is addressed to a method for the treatment of anoxidized cellulosic material in order to improve the thermal stabilityof the oxidized cellulosic material when used as a hemostatic material.The oxidized cellulose to be treated in accordance with the practice ofthe present invention may be derived from any of a wide variety ofcellulosic material, including but not limited to wood pulp, cotton,cotton linters, ramie, jute, paper, hemp, regenerated cellulose or rayonas well as a wide variety of others known to those skilled in the art.However, it is generally preferred to make use of cellulose in the formof cotton or regenerated cellulose, such as that prepared by the viscoseprocess, because of their greater purity. The oxidized cellulosicmaterial may be in the form of a knit or a woven fabric, such as gauzeor in a fibrous thread or film form.

The oxidized cellulosic material may be prepared by the selectiveoxidation using nitrogen dioxide, using a wide variety of techniques.For example, it is possible to form the oxidized cellulosic material bytreatment of the raw cellulosic material with liquid nitrogen dioxide inthe ratio of 1 part by weight cellulose per 5-1 ,000 parts by weightliquid nitrogen dioxide, and preferably 1 part by weight cellulosicmaterial to 25-50 parts by weight of the liquid nitrogen dioxide, asdisclosed in copending application, Ser. No. 745,221, filed July 16,1968, now U.S. Pat. No. 3,516,416, issued June 23, 1970. The reactiondescribed therein is carried out at a temperature of l5-65 C., and atautogenous pressure when the reaction temperature exceeds 21 C., theboiling point of nitrogen dioxide. Another method for effecting thisoxidation is disclosed in copending application, Ser. No. 745,135, filedJuly 16, 1968, now US. Pat. No. 3,491,766, issued Jan. 27, 1970, whereinthe oxidation reaction, including reaction rate and amount ofconversion, is materially improved by formulation of the oxidationreaction mixture to contain up to 8 percent by weight water in theliquid nitrogen dioxide system and by carrying out the reaction atelevated temperatures, generally about 15 C., and preferably within therange of 2045 C., depending somewhat upon the amount of moisture presentin the reaction medium, whereby the reaction medium is renderedrelatively non-electrically conductive so that the presence of water inthe reaction medium will not result in attack or degradation of thecellulosic material to be oxidized, and wherein the formulation toinclude aqueous medium in the reaction mixture of liquid nitrogendioxide also operates to adjust the specific gravity of the reactionmixture in the direction toward the specific gravity of the cellulosicmaterial whereby suspension of the cellulosic material in the reactionmedium is easier to achieve and maintain. The result is a more rapid anduniform oxidation reaction of the cellulosic material to produce ahigher quality product at a more rapid rage.

It is also possible, and frequently preferred in accordance with thepractice of the present invention, to employ an oxidized cellulose whichhas been prepared by the selective oxidation of cellulose with gaseousnitrogen dioxide or a mixture of gaseous nitrogen dioxide and nitricoxide. The reaction may be conveniently carried out by contacting thecellulose to be oxidized with the gaseous nitrogen oxide or oxides at atemperature within the range of 30-220 C. for a period of up to 40 hoursto oxidize at least percent of the methylol groups present in thecellulose molecule.

A further method for effecting the gaseous phase oxidation of celluloseis disclosed in copending application, Ser. No. 774,064, filed Nov. 7,1968, now US. Pat. No. 3,577,994, issued May II, 1971, wherein thecellulosic material is first wetted with a liquid nitrogen dioxide,which may optionally contain up to 8 percent by weight water, and thenis exposed to hot gaseous nitrogen dioxide. This particular method canbe advantageously used in the form of a continuous process for theproduction of large quantities of oxidized cellulosic material.

The concepts of the present invention reside in a process for thetreatment of oxidized cellulosic material, independent of the method bywhich the cellulosic material is oxidized, with a borohydride underalkaline conditions to improve the thermal stability of the treatedoxidized cellulose during storage. In accordance with the practice ofthe present invention, an oxidized cellulosic material is treated with aborohydride, such as ammonium borohydride, an alkali metal borohydride(e.g.,' lithium borohydride, sodium borohydride, potassium borohydride,etc.) or an alkaline earth metal borohydride e. g., magnesiumborohydride, calcium borohydride, etc.) at an alkaline pH. Thereafterthe treated oxidized cellulose is washed with dilute acid to destroy theborohydride, and then washed again with alcohol to remove any remainingacid and dried. It has been found that oxidized cellulosic materialstreated in this manner may be used as hemostatic materials which arecompletely stable at room temperatures, and can be stored for longperiods of time without the need to store under refrigerationconditions.

The treatment of the oxidized cellulosic material with the borohydridemay be conveniently carried out by placing the oxidized cellulosicmaterial in contact with a water-alcohol mixture, and then raising thepH of the resulting mixture to at least 8.5, and preferably to a pHwithin the range of 9-12 by adding thereto a base, such as an alkalimetal hydroxide or an ammonium hydroxide. Thereafter, the borohydridemay be added to the basic oxycellulose-water-alcohol mixture to providea ratio of 1 part by weight borohydride-for every l-lOO parts by weightof oxidized cellulose. The resulting solution containing the borohydridemay then be allowed to stand at a temperature within the range of 0-70C. for a period of 0.1 to 5 hours.

The water-alcohol mixture preferably comprises a mixture of water and analkanol having one to five carbon atoms, such as methanol, ethanol,isopropanol, etc., wherein the alcohol is present in an amountconstituting at least 20 percent by weight, and preferably 50-85 percentby weight, of the wateralcohol mixture. After the treatment with theborohydride has been completed, the treated oxidized cellulose may thenbe removed and washed with a dilute mineral acid, such as dilutehydrochloric acid or a mixture of dilute hydrochloric acid and analiphatic alcohol, to destroy the borohydride and to remove any metalsalts which may be present in the treated oxidized cellulosic material.Thereafter, the treated oxidized cellulosic material is preferablywashed again with an alcohol to remove any acid remaining. The treatedcellulose may then be dried and sterilized in a conventional manner,such as by the treatment of the oxidized cellulosic material withformaldehyde.

The following examples will serve to illustrate the principal conceptsof the present invention.

EXAMPLE 1 A piece of cotton gauze is oxidized by contacting it withgaseous nitrogen dioxide for a period of 25 hours at 20 C. After theoxidation reaction is completed, the gauze of oxidized cellulose iswashed with a mixture of equal parts by weight of water and ethanol toremove remaining nitrogen oxides and to prevent shrinkage.

Thereafter, the gauze of oxidized cellulose is immersed in a mixture of70 percent by weight methanol and 30 percent by weight water, and asufficient quantity of a solution of 0.5 N sodium hydroxide is added toraise the pH of the solution to about 10.5. Next, sodium borohydride isadded to the solution to provide a ratio of 0.1 parts by weight sodiumborohydride per 1 part oxidized cellulose. The oxidized cellulose isallowed to remain in contact with the borohydride solution for 1 hour atroom temperature, and then the treated oxidized cellulose is removedfrom the solution, washed with dilute hydrochloric acid, and washed withethanol.

The resulting product is dried and sterilized, and is found to haveexcellent stability at room temperatures.

It will be understood that the step of washing the oxidized cellulosicmaterial with an aliphatic alcohol, such as methanol, ethanol,isopropanol, or water, or mixtures thereof prior to the borohydridetreatment(the use of an ethanol-water mibtture as exemplified in Example1 is an optional step. It is frequently preferred to wash the oxidizedcellulosic material in this manner subsequent to oxidation in order toinsure the dimensional stability and thereby avoid shrinkage.

EXAMPLE 2 A gauze pad formed of rayon is wetted with liquid nitrogendioxide at ambient temperature and atmospheric pressure, and allowed todry until it has a dry appearance. Thereafter, the pad is exposed togaseous nitrogen dioxide at atmospheric pressure at a temperature of 70C. An oxidation level corresponding to oxidation of about 25 percent ofmethylol groups present is obtained.

Repetition of the foregoing cycle of wetting with nitrogen dioxide,drying and contacting with gaseous nitrogen dioxide is repeated untilthe oxidation level reaches at least 90 percent.

Thereafter, the pad is immersed in a methanol-water mixture containing65 percent by weight methanol, and the pH of the solution is raised byadding sufficient 0.5 N KOH until the pH is about 10. Then, sodiumborohydride is added to the solution in an amount to provide a ratio ofabout 0.2 parts by weight borohydride per 1 part of oxidized cellulose,and the oxidized cellulose is allowed to remain in contact with thesolution for a period of 50 minutes.

The treated oxidized cellulose is then removed from the solution, washedwith a dilute I-lCl-methanol mixture and washed again with ethanol.After drying and sterilization, the pad is found to have excellentstability at room temperatures.

EXAMPLE 3 A pad of cotton fibers is wetted with liquid nitrogen dioxidecontaining 2 percent water, and is then exposed, while still wet withliquid nitrogen dioxide, to hot gaseous nitrogen dioxide at 70 C. andatmospheric pressure. The cellulose is found to be 45 percent oxidizedbased upon the methylol groups in the cellulose.

The foregoing procedure is repeated until the cellulose is at leastpercent oxidized, and then the pad is washed with aqueous methanol.Thereafter, the pad is immersed in an ethanol-water mixture containing75 percent by weight methanol, and the pH of the solution is raised toabout 10 by adding 0.6 N NaOH.

Potassium borohydride is added, and the mixture is allowed to stand for1.5 hours at ambient temperatures. The treated oxidized cellulose isremoved from the solution, washed in the manner shown in Example 1 driedand sterilized.

The hemostatic materials of oxidized cellulose treated in accordancewith the practice of the invention are susceptible to a wide variety ofuses. Oxidized cellulose treated in accordance with the presentinvention is a natural hemostat, and forms, when contacted with humanblood, a dark gellatinous mass which in effect serves as an artificialclot within the area of the bleeding within a few minutes from the timethe oxidized cellulose is applied.

One of the principal advantages of the use of an oxidized cellulosetreated in accordance with the concepts of the present invention is thatit gradually dissolves and/or absorbed by body fluid which makes itpossible to utilize hemostatic materials formed of the material inclosed wounds without the concomitant occurrence of an adverse tissuereaction.

The hemostatic materials of the present invention in the form of knittedfabrics, carded fiber pads, sutures and like articles have broadapplication in any type of surgery,and in other situations where thecontrol of bleeding is required. The material is placed in contact withthe bleeding vessel whereby a clot forms within a few minutes. The woundmay be, if conditions dictate, closed with the hemostatic material inplace, and the hemostat will be dissolved by body fluids. Alternatively,the material may be removed after a clot has formed without sticking ofthe material to the wound or renewed bleeding since the portion of thematerial directly in contact with the wound has dissolved.

it will be apparent from the foregoing that the present inventionprovides a new and improved oxidized cellulosic material which may beused as a hemostatic material having heretofore unattainable stability,and which may be prepared by a simple and economic process without theneed to employ expensive reagents.

It will be understood that various changes and modifications may be madein the details of formulation and procedure and use which provide thecharacteristics of the invention without departing from the spiritthereof, particularly as defined in the following claims.

We claim:

1. In the method of stabilizing a hemostatic material consisting of anoxycellulose pad, the improvement comprising immersing said oxycellulosepad in an aqueous alcoholic solution containing a borohydride for aperiod of from 0.1 to 5 hours at a temperature of from 0 to 70 C. and apH of 9-12.

2. A process as defined in claim 1 wherein said borohydride is sodiumborohydride.

3. A process as defined in claim 1 wherein said solution contains atleast 20 percent by weight of alcohol.

4. in the method of stabilizing a hemostatic material consisting of acellulosic pad, the improvement comprising first oxidizing saidcellulosic gauze pad with nitrogen dioxide and thereafter immersing saidcellulosic pad in an aqueous alcoholic solution at a pH of from 9-12wherein said solution contains an alkali borohydride.

dioxide is in the liquid phase.

6. A process as defined in claim 4 wherein said nitrogen dioxide is inthe gaseous phase.

2. A process as defined in claim 1 wherein said borohydride is sodiumborohydride.
 3. A process as defined in claim 1 wherein said solutioncontains at least 20 percent by weight of alcohol.
 4. In the method ofstabilizing a hemostatic material consisting of a cellulosic pad, theimprovement comprising first oxidizing said cellulosic gauze pad withnitrogen dioxide and thereafter immersing said cellulosic pad in anaqueous alcoholic solution at a pH of from 9-12 wherein said solutioncontains an alkali borohydride.
 5. A process as defined in claim 4wherein said nitrogen dioxide is in the liquid phase.
 6. A process asdefined in claim 4 wherein said nitrogen dioxide is in the gaseousphase.